Prior art panel benders are known which operate the process for bending a sheet of sheet metal using a pair of blades mounted on a substantially C-shaped structure and which may be hydraulically or electro-mechanically operated.
In this type of machine, a sheet metal sheet to be bent is clamped by a device, the so-called presser or pressure bar, which moves in a direction at right angles to the plane of the metal sheet itself and it is compressed against a fixed part, the so-called counterblade.
Each of the two blades, upper and lower, describes a curvilinear trajectory in the two degrees of horizontal (X) and vertical (Y) freedom, in directions parallel and at right angles to, respectively, the plane of the metal sheet.
During the movement the blade enters into contact with the metal sheet and deforms it plastically. The trajectory may be fixed or in some cases programmed with numerical control systems (NCS), by interpolation of the two axes X, Y.
The prior art architectures of the kinematic chains of the blade holder are as follows:
a) articulated pentalateral with two degrees of freedom in which the movement elements are hydraulic cylinders which extend in length;
b) articulated pentalateral in which the movement elements are cranks operated by an electric motor coupled with precision reduction gear for high torques. This solution is described in patent document WO-A-2006/043292;
c) wedge-shaped slide coupled with the blade holder structure through a plane inclined at a suitable angle, in which the movement at right angles to the plane of the metal sheet is provided by a linear actuator which moves the blade holder together with the above-mentioned slide; the movement in the direction parallel to the metal sheet is provided by the relative movement between the blade holder and the slide itself. This solution is described in patent document Wo-A-98/046380;
The main drawback of the first two solutions a) and b) derives from the kinematic complexity of the mechanism, which requires the development of inverse kinematic calculations, that may often only be solved with the use of particular algorithms.
Another drawback often derives from the reduced number of supports and constraints of the C-shaped structure of the blade holder which deforms under the bending load, in addition to the fact that the blades move in a non-parallel manner with a roto-translatory motion
These limitations are partly superseded by the third solution c), which however has an economic limitation in the making of an electro-mechanical operating system with screw, gearmotor and motor.
The bending load is supported completely by the linear actuator which moves the C-shaped structure of the blade holder in a direction at right angles to the plane of the metal sheet.
In the direction parallel to the plane of the metal sheet the load is reduced thanks to the interposing of the wedge-shaped slide.